The present invention relates to the field of communications. More particularly, the invention relates to an RF safety-conscious high-gain antenna communications system. However, the invention could also be applied in other fields such as navigation where similar high-gain antenna systems are used.
High-gain communication systems are utilized for a wide variety of applications, including, for example, satellite communications, terrestrial wireless networks, microwave dishes, and other point-to-point or multipoint operations. These applications all involve the use of a high-frequency antenna system. It frequently becomes necessary for users or maintenance personnel to service the transmitting antenna. Exposure to the high-powered signal can be undesirable for these persons. Thus, some protective mechanism may be helpful in these situations. In other instances, people may stray in front of the antenna face, particularly if these systems are deployed in homes. It may be desirable to detect the presence of these persons, both to reduce power to the system and to prevent trespassing.
These events give rise to the problems addressed by the present invention--reducing exposure of maintenance personnel and other persons who stray too close to the antenna, to RF transmissions, and, alternatively, providing a means to alert the system controller to the presence of intruders.
While microwave proximity detectors are well known in the art, use of these systems would employ at least two independent RF sources. One RF source is used to transmit the high-gain signal for the intended communications application. The other RF source is used to detect the presence of foreign objects in front of the communications antenna. The second RF source emits a signal in the direction of the communications antenna's line-of-sight while concurrently monitoring the presence of any reflected energy which would indicate some obstruction.
Drawbacks accompany this approach. For example, the use of two RF sources to implement the safety/security mechanism requires the expenditure of additional energy to run the communications system. Further, each RF source is associated with its own independent circuit elements such as circulators, antennas, isolators, mixers, etc. The maintenance of two RF sources and their associated components is therefore required, rendering this approach less efficient and compact. Still another problem with this method is that the second RF source can potentially interfere with the signal transmitted by the first RF source, thereby injecting unnecessary electrical noise into the transmitted communications signal. The second RF source may also interfere with an ordinary communications signal which is received by the main antenna. And, there is also the additional cost of the second RF source. In light of these drawbacks, it is desirable to implement a communications system which integrates a proximity detector without the addition of a second RF source.
Accordingly, it is an object of the invention to implement, in a system using a single RF source, a safety or security mechanism for reducing or terminating power to a high-gain antenna, or for initiating a security function, when objects are detected in front of the antenna.
Another object of the invention is to create a more compact and robust proximity detector which uses fewer structures and components.
Another object of the invention is to implement a proximity detector designed to facilitate communications with minimal interference from extraneous electrical sources.
Another object of the invention is implement a proximity detector having a single RF source and capable of detecting objects located in a designated range and/or traveling at a specified velocity.